1. Technical Field
The present invention relates to an electronic device, a liquid ejecting head, and a manufacturing method for an electronic device employed, for example, to eject liquid from a liquid ejecting head such as an ink jet recording head. In particular, the invention relates to an electronic device, a liquid ejecting head, and an electronic device manufacturing method in which plural substrates are joined together using an adhesive.
2. Related Art
Electronic devices employed in liquid ejecting heads include those in which plural substrates are joined together in a stacked state using an adhesive. Such electronic devices are provided with liquid flow paths in communication with nozzles, and movable regions that cause pressure fluctuations in the liquid in the liquid flow paths so as to eject the liquid through the nozzles. For example, an ink jet recording head described in JP-A-11-227190 describes an electronic device stacked with a substrate formed with a pressure chamber, a diaphragm that blocks off one open face of the pressure chamber, and a piezoelectric element that displaces a movable region of the diaphragm corresponding to the pressure chamber. In this configuration, a silicon single crystal substrate (referred to simply as a silicon substrate below) is employed as the substrate formed with the pressure chamber, and the pressure chamber is formed by etching the silicon substrate. In a process in which a mask used in formation of the pressure chamber is removed by wet etching, the diaphragm (insulating film) revealed inside the pressure chamber is exposed to the etching liquid such that the diaphragm is also etched (isotropic etching) up to partway along its thickness direction. Side etching (undercutting) then advances to below walls bounding the pressure chamber, resulting in eave portions being formed at opening edges on the diaphragm side of the pressure chamber.
In the configuration described in JP-A-11-227190, the diaphragm undergoes side etching beyond the opening edges of the pressure chamber, thereby enlarging the area of the movable region of the diaphragm that is displaced by the drive of the piezoelectric elements by a commensurate amount in comparison to configurations in which the diaphragm is not etched (a configuration in which the area of the movable region is substantially the same as the area of a pressure chamber opening). The thickness of the movable region is moreover thinner than the thickness of other portions of the diaphragm. Damage such as cracking is thereby liable to occur in the diaphragm as a result of displacement of the movable region. Since the area and thickness of the portion that in effect functions as the movable region is dependent on etching precision, there is a possibility that variation could occur between the oscillation characteristics of respective movable regions (for example, the displacement amount and natural oscillation frequency when applied with a uniform external force).